Rx7 oil cooler thermostats open at 65'C / 150F and should be fully open by 82'C / 180F. 65-85C is therefore a normal operating zone when warm.

Anything over 95'C / 205F is danger zone according to Racing Beat. I have read tgat for the FD, 250F at the sump was the maximum tolerable limit when measured at the sump but was later revised down to 210F